The demand for techniques for holding food at selected temperatures and moisture levels for extended periods of time is widespread in the fast food industry. In this industry it is particularly important to maintain uniformity of heating within closely controlled ranges and introduce the proper amount of moisture into the heated chamber containing the food either to reconstitute the food or maintain a desired moisture level. Of particular importance in heating food is the avoidance of passing a significant air flow in direct contact with the food, which has deleterious effects particularly as it relates to drying out the food.
In earlier filed applications now U.S. Pat. Nos. 3,868,941 and 3,955,007, assigned to the assignee of the present invention, there is described one form of apparatus and method for holding food and the like wherein a relatively still volume of air is confined about a food using metal heat-conductive imperforate walls and an open passage around the walls maintains a flow of air heated by a gas burner below the confined volume of air in a generally outward, upward and inward course of travel with a top exhaust into the atmosphere. This circulation of the heated air is along the bottom, both sides and the top of the confined, still volume of air so as to be along at least two pairs of perpendicular axes and over major portions of the confined volume of air and produces substantially uniform heating of the volume of air and thereby the food contained therein by conduction and convection without a direct contact of the heated air flow with the food, which might otherwise cause undue drying out of the food.
In yet another U.S. application Ser. No. 536,456, filed Dec. 26, 1974, entitled "Display Apparatus and Method for Holding Food and the Like", assigned to the assignee of the present invention, there is described another form of apparatus and method wherein a relatively still volume of air is confined about a food within a flow of heated moisturized air directed in a vortex-like pattern with the still volume of air being the core of the vortex-like pattern and this pattern conveys heat and moisture to the core containing the food. Again this circulation of the heated air is along both sides, the front and rear walls forming the chamber so that heating takes place along at least two pairs of perpendicular axes and over a major portion of the volume of gas being heated and again produces substantially uniform heating without appreciable localized or spot heating at any one place and without a significant direct contact of the heated air flow with the food.
In both forms above described, a controllable source of moisture introduces controlled quantities of moisture into the confined volume of air during heating.
Accordingly, it is an object of this invention to provide a novel apparatus and method of holding food and the like at desired temperature levels utilizing a closed passage for circulating heated gases to transmit heat to the food while it is maintained in a substantially static or still volume of air with no substantial direct contact of air flow of heated gases with the food.
Yet another object of the present invention is to provide a novel apparatus and method of holding food and the like characterized by a closed heating, recirculating passage for maintaining a flow of heated air of a selected temperature about a volume of air along at least two pairs of perpendicular axes and about a major portion of the volume of air being heated to provide substantially uniform heating by conduction and convection.
Still a further object of the present invention is to provide a novel apparatus and method of holding food and the like that may be advantageously powered by electricity.